Abstract of paper in Proceedings of the National Academy of Science
92:5032-5036, 1995.
Disruption of the gene for hsp30, an alpha-crystallin-related
heat shock protein of Neurospora crassa, causes defects in
thermotolerance
Nora Plesofsky-Vig and Robert Brambl
Departments of Genetics and Cell Biology and Plant Biology and
Plant Molecular Genetics Institute
The University of Minnesota
ABSTRACT
The alpha-crystallin-related heat shock proteins are produced by all
eukaryotes, but the role of these proteins in thermoprotection
remains unclear. To investigate the function of one of these
proteins, we disrupted expression of the single-copy hsp30 gene of
Neurospora crassa, using RIP (Repeat-Induced Point) mutagenesis, and
we generated and characterized mutant strains that were deficient in
hsp30 synthesis. These strains grew well at high temperature and they
acquired heat shock-induced thermotolerance. However, the
hsp30-defective strains proved to be extremely sensitive to the
combined stresses of high temperature and carbohydrate limitation,
enforced by the addition of a glucose analogue. Under these
conditions, their survival was reduced to as low as 10% that of
wild-type cells. This sensitive phenotype was reversed by
reintroduction of a functional hsp30 gene into the mutant strains.
The mutant cells showed altered localization of a 22 kDa protein,
which was easily solubilized from their mitochondria, in contrast to
its retention by the mitochondria of wild-type cells. Antibodies
against hsp30 coimmunoprecipitated a protein of approximately 22 kDa
from wild-type cells. These results suggest that hsp30 may be
important for efficient carbohydrate utilization during high
temperature stress and that it may function as a protein chaperone in
vivo.